Changes In Fundamental Frequency Research Articles

Uncertainty in location, level and fundamental frequency results in informational masking in a vowel discrimination task for young and elderly subjects

Informational masking (IM) is defined as the compromised ability to perceive and analyze signals from a single sound source in a cacophony of sounds from other sources even if the excitation patterns produced by these signals in the auditory periphery are well separated from those produced by the sounds from the other sources. IM that causes an elevation of discrimination thresholds is affected by the similarity between target and masker and by stimulus uncertainty. Here, six young and six elderly subjects were asked to discriminate between sequentially presented reference and target vowels of the vowel pairs /I/-/i/, /æ/-/ε/, and /α/-/Λ/. Psychometric functions were collected characterizing the discrimination of target vowels from reference vowels. Target vowels differed from the reference by one of seven steps shifting the three formants of a reference vowel towards the formants of the corresponding target vowel. Stimulus statistics were varied, generating uncertainty by non-informative but potentially distracting location, level, and fundamental frequency changes or all three combined. Young subjects tested with distracting changes applied to the target vowels only, the reference vowels only, or the target and reference vowels showed similar amounts of IM for all three conditions. Elderly subjects were tested with distracting changes applied to target vowels only. Applying uncertainty only to the target vowels led to worse vowel discrimination thresholds for young and elderly subjects and thresholds increased most for the three distracting changes combined. Elderly subjects showed higher vowel discrimination thresholds than young subjects, but the increase in vowel discrimination thresholds due to IM did not differ between young and elderly subjects. The temporal fine structure processing of elderly subjects was degraded in comparison to young subjects, but it was only correlated with the discrimination threshold for vowel pair /I/-/i/.

한국어-영어 이중언어 화자의 사용 언어, 문맥, 언어 능숙도에 따른 기본 주파수 변화*

The purpose of this study is to determine whether the mean fundamental frequency (F0) changes depending on language, task, or language proficiency for Korean-English bilinguals. A total of forty-eight Korean-English speakers (28 balanced bilinguals and 20 Korean dominant bilinguals) participated in the study. Participants were asked to read aloud two types of tasks in English and Korean. For statistical analyses, the language × task two-way repeated ANOVAs were conducted within the balanced bilingual group first, and then group × language two-way mixed ANOVAs. The results showed that the females in both bilingual groups changed their mean F0 depending on the language they used and the tasks (<italic>p</italic>&lt;.05), whereas no significant results were found in the males in either group under any conditions. The mean fundamental frequency in the Korean reading task was significantly higher than that in the English reading task for females in both balanced and Korean dominant bilingual groups. Thus, changes in mean F0 depending on language and context may reflect gender-specific characteristics, and females seem to be more sensitive to the socio-cultural standards that are imposed on them.

Just-noticeable differences of fundamental frequency change in Mandarin-speaking children with cochlear implants

Fundamental frequency (F0) provides the primary acoustic cue for lexical tone perception in tonal languages but is poorly presented in cochlear implants (CIs). Currently, there is still a lack of understanding on the sensitivity to F0 information in CI users speaking tonal languages. In the present study, just-noticeable differences (JNDs) of F0 contour and F0 level change in Mandarin-speaking kindergarten-aged children with CIs were measured and compared with those in age-matched normal-hearing (NH) peers. Statistical analysis showed that both JND of F0 contour change (JND-C) and JND of F0 level change (JND-L) were significantly larger in CI group than in NH group. Furthermore, within-group comparison of JND-C and JND-L found that JND-C was significantly smaller than JND-L among children with CIs; however, opposite pattern was observed among children with normal hearing. The contrary sensitivity to F0 contour and F0 level change between children with CIs and children with normal hearing suggest discrepant mechanisms of F0 processing in these two groups as a result of hearing experience.Fundamental frequency (F0) provides the primary acoustic cue for lexical tone perception in tonal languages but is poorly presented in cochlear implants (CIs). Currently, there is still a lack of understanding on the sensitivity to F0 information in CI users speaking tonal languages. In the present study, just-noticeable differences (JNDs) of F0 contour and F0 level change in Mandarin-speaking kindergarten-aged children with CIs were measured and compared with those in age-matched normal-hearing (NH) peers. Statistical analysis showed that both JND of F0 contour change (JND-C) and JND of F0 level change (JND-L) were significantly larger in CI group than in NH group. Furthermore, within-group comparison of JND-C and JND-L found that JND-C was significantly smaller than JND-L among children with CIs; however, opposite pattern was observed among children with normal hearing. The contrary sensitivity to F0 contour and F0 level change between children with CIs and children with normal hearing suggest discrepan...

Cortical Correlates of Attention to Auditory Features.

Pitch and timbre are two primary features of auditory perception that are generally considered independent. However, an increase in pitch (produced by a change in fundamental frequency) can be confused with an increase in brightness (an attribute of timbre related to spectral centroid) and vice versa. Previous work indicates that pitch and timbre are processed in overlapping regions of the auditory cortex, but are separable to some extent via multivoxel pattern analysis. Here, we tested whether attention to one or other feature increases the spatial separation of their cortical representations and if attention can enhance the cortical representation of these features in the absence of any physical change in the stimulus. Ten human subjects (four female, six male) listened to pairs of tone triplets varying in pitch, timbre, or both and judged which tone triplet had the higher pitch or brighter timbre. Variations in each feature engaged common auditory regions with no clear distinctions at a univariate level. Attending to one did not improve the separability of the neural representations of pitch and timbre at the univariate level. At the multivariate level, the classifier performed above chance in distinguishing between conditions in which pitch or timbre was discriminated. The results confirm that the computations underlying pitch and timbre perception are subserved by strongly overlapping cortical regions, but reveal that attention to one or other feature leads to distinguishable activation patterns even in the absence of physical differences in the stimuli.SIGNIFICANCE STATEMENT Although pitch and timbre are generally thought of as independent auditory features of a sound, pitch height and timbral brightness can be confused for one another. This study shows that pitch and timbre variations are represented in overlapping regions of auditory cortex, but that they produce distinguishable patterns of activation. Most importantly, the patterns of activation can be distinguished based on whether subjects attended to pitch or timbre even when the stimuli remained physically identical. The results therefore show that variations in pitch and timbre are represented by overlapping neural networks, but that attention to different features of the same sound can lead to distinguishable patterns of activation.

Reduced left-lateralized pattern of event-related EEG oscillations in infants at familial risk for language and learning impairment.

The ability to rapidly discriminate successive auditory stimuli within tens-of-milliseconds is crucial for speech and language development, particularly in the first year of life. This skill, called Rapid Auditory Processing (RAP), is altered in infants at familial risk for language and learning impairment (LLI) and is a robust predictor of later language outcomes. In the present study, we investigate the neural substrates of RAP, i.e., the underlying neural oscillatory patterns, in a group of Italian 6-month-old infants at risk for LLI (FH+, n = 24), compared to control infants with no known family history of LLI (FH−, n = 32). Brain responses to rapid changes in fundamental frequency and duration were recorded via high-density electroencephalogram during a non-speech double oddball paradigm. Sources of event-related potential generators were localized to right and left auditory regions in both FH+ and FH− groups. Time-frequency analyses showed variations in both theta (Ɵ) and gamma (ɣ) ranges across groups. Our results showed that overall RAP stimuli elicited a more left-lateralized pattern of oscillations in FH− infants, whereas FH+ infants demonstrated a more right-lateralized pattern, in both the theta and gamma frequency bands. Interestingly, FH+ infants showed reduced early left gamma power (starting at 50 ms after stimulus onset) during deviant discrimination. Perturbed oscillatory dynamics may well constitute a candidate neural mechanism to explain group differences in RAP. Additional group differences in source location suggest that anatomical variations may underlie differences in oscillatory activity. Regarding the predictive value of early oscillatory measures, we found that the amplitude of the source response and the magnitude of oscillatory power and phase synchrony were predictive of expressive vocabulary at 20 months of age. These results further our understanding of the interplay among neural mechanisms that support typical and atypical rapid auditory processing in infancy.

The Prosodic Marionette: A method to visualize speech prosody and assess perceptual and expressive prosodic abilities

Speech technology applications have emerged as a promising method for assessing speech-language abilities and at-home therapy, including prosody. Many applications assume that observed prosody errors are due to an underlying disorder; however, they may be instead due to atypical representations of prosody such as immature and developing speech motor control, or compensatory adaptations by those with congenital neuromotor disorders. The result is the same – vocal productions may not be a reliable measure of prosody knowledge. Therefore, in this study we examine the usability of a new technology application to express prosody knowledge without relying on vocalizations using the Prosodic Marionette (PM) graphical user interface for artificial resynthesis of speech prosody. We tested the ability of neurotypical participants to use the PM interface to control prosody through 2D movements of word-icon blocks vertically (fundamental frequency), horizontally (pause length), and by stretching (word duration) to correctly mark target prosodic contrasts. Nearly all participants used vertical movements to correctly mark fundamental frequency changes where appropriate (e.g., raised second word for pitch accent on second word). A smaller percentage of participants used the stretching feature to mark duration changes; when used, participants correctly lengthened the appropriate word (e.g., stretch the second item to accent the second word). Our results suggest the PM interface can be used reliably to correctly signal speech prosody, which validates future use of the interface to assess prosody in clinical and developmental populations with atypical speech motor control.

Social isolation alters ultrasonic vocalizations but not thyroarytenoid neuromuscular junctions in old rats.

Age-related muscle atrophy of the laryngeal muscles contributes to presbyphonia. Remodeling of the neuromuscular junction is one aspect underlying age-related muscle atrophy. Although muscle disuse has been shown to exacerbate age-related neuromuscular changes in the limb muscles, it is unknown if reduced vocal use has a similar effect in the laryngeal muscles. The objective of this study was to examine the use of social isolation as a novel method to reduce vocal use in old rats-and the impact of that reduced vocal use on ultrasonic vocalization acoustics and neuromuscular junction morphology in the thyroarytenoid muscle. Animal group comparison. Old F344/BN rats (31 months of age) were socially isolated (n = 8) or communally housed (n = 8) for 8 weeks. Effect of housing condition on ultrasonic vocalization acoustics was assessed by calculating the changes in vocalization fundamental frequency and amplitude from baseline to 8 weeks. Neuromuscular junction morphology was measured in the lateral and medial portions of the thyroarytenoid muscle at the conclusion of the experiment. Vocalization amplitude decreased by a mean of -4.4 dB (standard deviation [SD], 4.49) after social isolation, whereas amplitude increased by a mean of 5.7 dB (SD, 5.07) in the communally housed rats (P = 0.002). There was no significant difference in the change in fundamental frequency between groups. Furthermore, there were no group differences in any measure of neuromuscular junction morphology. These results suggest that neuromuscular junctions in the thyroarytenoid muscle of old rats are unaffected by 8 weeks of social isolation, despite functional changes in vocalizations. NA Laryngoscope, 129:E9-E14, 2019.

Work-related communicative profile of radio broadcasters: a case study

Purpose: To explore the short-term effect of work-related voice use on voice function, and noise exposure on hearing function among radio broadcasters.Method: A 1-week follow-up study with the participation of two radio broadcasters was conducted. Participants were monitored at the beginning and at the end of the working week. Premonitoring assessment on Monday (baseline measure) and postmonitoring assessment on Friday (follow-up measure) were performed to identify short-term effects of work-related conditions on voice and hearing function among radio broadcasters.Result: Changes in fundamental frequency postmonitoring at the end of the work week may be an indication of work-related vocal fatigue. Changes in the distribution and standard deviation of SPL during the monitoring from Monday to Friday may indicate control of the vocal loudness as a strategy to reduce vocal effort during broadcasting. During a 1-week follow-up, noise conditions during radio broadcasting were below occupational exposure limits and without noticeable consequences on hearing function.Conclusion: The work-related communicative profile of radio broadcasting, from this pilot study, suggests that although vocal demands in terms of vocal load may differ among broadcasters, the work-related conditions of broadcasting may play a role on vocal function among these occupational voice users. Concerning hearing function, our results indicate that occupational noise exposure represented minimal risk for hearing problems but the consequences of long-term noise exposure on hearing mechanisms may yet occur. Future studies with bigger sample sizes are warranted to confirm our results.

Comparison of Ultrasonic Methods for Thermally Damaged Concrete Nondestructive Testing

Behaviour of concrete under elevated temperatures is very complex. There is a change of mechanical and physical parameters with temperature. In this paper we study the relations of thermal damage processes in concrete and parameters obtained by different ultrasonic methods. The concrete specimens were heated in programmable laboratory furnace. Selected temperature (200°C, 400°C, 600°C, 800°C, 1000°C and 1200°C) were maintained for 60 minutes. The first ultrasonic measurement technique in this paper was Ultrasonic Pulse Velocity method. The pulse velocity in a concrete depends on its density and its elastic properties. Therefore, it is possible to deduce the quality and the compressive strength of the concrete from the ultrasonic pulse velocity. The second ultrasonic measurement technique in this paper uses broadband pulse-compression signal, with variable amplitude to measure the change of fundamental frequency. This method is based on Nonlinear Elastic Wave Spectroscopy. Nonlinear Elastic Wave Spectroscopy methods takes advantage of the fact, that nonlinearities in material manifest themselves as a resonant frequency shifts and harmonics or dumping coefficients changes. The progress of nondestructive testing parameters was confirmed by results from the destructive tests.

Switch of synchronization states of aeroacoustical coupled organ pipes

The separation distance of two equally tuned, aeroacoustically coupled organ pipes is varied stepwise in a synchronization experiment. At distances of multiples of about half the wavelength of the fundamentals, abrupt changes of SPL and fundamental frequency of the coupled and synchronized system can be observed. Frequency jumps also occur at higher harmonics. The nonlinear coupling function of the system implicitly takes into account the time delay of the system caused by the separation distance and therefore plays an important role for the observed phenomenon. The effect can be explained as a switch of synchronization states from in-phase to anti-phase and vice versa.

Piezoelectric Lead Zirconate Titanate (PZT) Ring Shaped Contour-Mode MEMS Resonators

Flexibility in setting fundamental frequency of resonator independent of its motional resistance is one of the desired criteria in micro-electromechanical (MEMS) resonator design. It is observed that ring-shaped piezoelectric contour-mode MEMS resonators satisfy this design criterion than in case of rectangular plate MEMS resonators. Also ring-shaped contour-mode piezoelectric MEMS resonator has an advantage that its fundamental frequency is defined by in-plane dimensions, but they show variation of fundamental frequency with different Platinum (Pt) thickness referred as change in ratio of fNEW/fO. This paper presents the effects of variation in geometrical parameters and change in piezoelectric material on the resonant frequencies of Platinum piezoelectric-Aluminium ring-shaped contour-mode MEMS resonators and its electrical parameters. The proposed structure with Lead Zirconate Titanate (PZT) as the piezoelectric material was observed to be a piezoelectric material with minimal change in fundamental resonant frequency due to Platinum thickness variation. This structure was also found to exhibit extremely low motional resistance of 0.03 Ω as compared to the 31-35 Ω range obtained when using AlN as the piezoelectric material. CoventorWare 10 is used for the design, simulation and corresponding analysis of resonators which is Finite Element Method (FEM) analysis and design tool for MEMS devices.

Enhancement of high-order harmonics in a plasma waveguide formed in clustered Ar gas.

Generation of high-order harmonics (HHs) is intensified by using a plasma waveguide created by a laser in a clustered gas jet. The formation of a plasma waveguide and the guiding of a laser beam are also demonstrated. Compared to the case without a waveguide, harmonics were strengthened up to nine times, and blue-shifted. Numerical simulation by solving the time-dependent Schrödinger equation in strong field approximation agreed well with experimental results. This result reveals that the strengthening is the result of improved phase matching and that the blue shift is a result of change in fundamental laser frequency due to self-phase modulation (SPM).

Immediate Effects of External Vibration vs Placebo on Vocal Function Therapy in Singers

External vibration therapy (EVT) has been widely used in chronic pain conditions, musculoskeletal rehabilitation, and athletic training. Vibration therapy has been suggested to enhance vocal performance and has been popularized in social media. However, there is no evidence to support its effect on vocal function. To evaluate the immediate effects of EVT in trained singers using acoustic and self-assessment parameters. Prospective, randomized, placebo-controlled interventional study at St Michael's Hospital Voice Clinic, affiliated with the University of Toronto. Data collection and analysis were performed by investigators who were blinded to the group assignment of the participants. Study participants were randomized to EVT or a placebo (control) group. The study dates were September 2015 to December 2016. Participants attended the voice laboratory at St Michael's Hospital, where a standardized data collection protocol was performed, including acoustic parameters, voice range profile, and soft voice tasks, followed by subjective rating of vocal effort or discomfort. The EVT group underwent EVT to 5 neck sites bilaterally. The placebo group underwent the same protocol with a modified device. After the intervention, the participants repeated the standardized data collection. The primary outcome in this study was acoustic analysis (jitter, shimmer, and pitch range) compared before and after treatment. In addition, secondary outcomes included perceived effort or discomfort evaluated by participants after 4 voice tasks proposed to investigate more subtle voice properties. Within and between groups, data sets were statistically analyzed for potential treatment effect. Among 27 participants (age range, 18-50 years; all female), 14 were randomized to the intervention group and 13 to the placebo group. Comparison of the treatment effect on the vowel token acoustic parameters evaluated showed that, after EVT, participants had a more cohesive change with a restricted 95% CI compared with placebo. The mean change in fundamental frequency after intervention was 5.00 Hz in both groups but the 95% CI was much wider after placebo (-30.30 to 19.20) than after EVT (-18.10 to 7.50). After EVT, the effect size was notable in the vowel (0.83) and SVT3 (0.79) task. In this study, EVT demonstrated a more predictable change in acoustic metrics compared with the placebo treatment. Effort ratings for 6 voice tasks evaluated in this study were not found to be different after EVT compared with the placebo treatment. clinicaltrials.gov Identifier: NCT02083341.

Empirical validation of a novel operationalization of the expression of emotion: A case of synchronization of relative pitch height and evaluative language across elements of discourse structure in a narrator with Broca’s aphasia

Empirical validation of a novel operationalization of the expression of emotion: A case of synchronization of relative pitch height and evaluative language across elements of discourse structure in a narrator with Broca’s aphasia

Acoustical and perceptual study of voice disguise by age modification in speaker verification

The task of speaker recognition is feasible when the speakers are co-operative or wish to be recognized. While modern automatic speaker verification (ASV) systems and some listeners are good at recognizing speakers from modal, unmodified speech, the task becomes notoriously difficult in situations of deliberate voice disguise when the speaker aims at masking his or her identity. We approach voice disguise from the perspective of acoustical and perceptual analysis using a self-collected corpus of 60 native Finnish speakers (31 female, 29 male) producing utterances in normal, intended young and intended old voice modes. The normal voices form a starting point and we are interested in studying how the two disguise modes impact the acoustical parameters and perceptual speaker similarity judgments.First, we study the effect of disguise as a relative change in fundamental frequency (F0) and formant frequencies (F1 to F4) from modal to disguised utterances. Next, we investigate whether or not speaker comparisons that are deemed easy or difficult by a modern ASV system have a similar difficulty level for the human listeners. Further, we study affecting factors from listener-related self-reported information that may explain a particular listener’s success or failure in speaker similarity assessment.Our acoustic analysis reveals a systematic increase in relative change in mean F0 for the intended young voices while for the intended old voices, the relative change is less prominent in most cases. Concerning the formants F1 through F4, 29% (for male) and 30% (for female) of the utterances did not exhibit a significant change in any formant value, while the remaining ∼ 70% of utterances had significant changes in at least one formant.Our listening panel consists of 70 listeners, 32 native and 38 non-native, who listened to 24 utterance pairs selected using rankings produced by an ASV system. The results indicate that speaker pairs categorized as easy by our ASV system were also easy for the average listener. Similarly, the listeners made more errors in the difficult trials. The listening results indicate that target (same speaker) trials were more difficult for the non-native group, while the performance for the non-target pairs was similar for both native and non-native groups.

A comparison of two endoscopic posterior cordotomy techniques: Laser cordotomy vs diathermy-assisted cordotomy.

To compare respiratory function, swallowing and voice quality of bilateral abductor vocal fold paralysis (BAVFP) patients undergoing laser and diathermy-assisted posterior cordotomy. Prospective study. Tertiary academic hospital. Thirty patients were included in the study (groups 1 and 2, 15 patients each). Mean age was 53 ± 14.27 years with a range of 31-78 years (12 [40%] males, 18 [60%] females). Sufficient airway, complications, FEV1, FEV1/FVC, peak expiratory flow rate (PEF), voice quality VAS, fundamental frequency, jitter, shimmer, NHR, amplitude perturbation quotient (APQ) and pitch perturbation quotient (PPQ) scores. A sufficient laryngeal airway was achieved in all patients. Six patients (20%) developed postoperative granulation tissue (2 in group 1 and 4 in group 2). There was a statistically significant improvement in FEV1, FEV1/FVC and PEF measurements at the postoperative sixth month compared to preoperative measurements in both of the groups (P < .05). Preoperative median voice quality VAS scores in groups 1 and 2 were 8 (IQR = 1) and 8 (IQR = 3), respectively. Postoperative sixth-month voice quality VAS scores in groups 1 and 2 were 6 (IQR = 1) and 6 (IQR = 0), respectively. Postoperative VAS scores were significantly lower in both groups (P < .05). The postoperative changes in fundamental frequency, NHR, jitter, shimmer, APQ and PPQ were not statistically significant in both of the groups (P > .05). Laser and diathermy-assisted posterior cordotomy are both minimally invasive, effective techniques with a long-term sufficient laryngeal airway. Despite lower quality of voice VAS scores, objective acoustic outcomes were not significantly lower in both of the groups.

Grasshopper mice employ distinct vocal production mechanisms in different social contexts.

Functional changes in vocal organ morphology and motor control facilitate the evolution of acoustic signal diversity. Although many rodents produce vocalizations in a variety of social contexts, few studies have explored the underlying production mechanisms. Here, we describe mechanisms of audible and ultrasonic vocalizations (USVs) produced by grasshopper mice (genus Onychomys). Grasshopper mice are predatory rodents of the desert that produce both loud, long-distance advertisement calls and USVs in close-distance mating contexts. Using live-animal recording in normal air and heliox, laryngeal and vocal tract morphological investigations, and biomechanical modelling, we found that grasshopper mice employ two distinct vocal production mechanisms. In heliox, changes in higher-harmonic amplitudes of long-distance calls indicate an airflow-induced tissue vibration mechanism, whereas changes in fundamental frequency of USVs support a whistle mechanism. Vocal membranes and a thin lamina propria aid in the production of long-distance calls by increasing glottal efficiency and permitting high frequencies, respectively. In addition, tuning of fundamental frequency to the second resonance of a bell-shaped vocal tract increases call amplitude. Our findings indicate that grasshopper mice can dynamically adjust motor control to suit the social context and have novel morphological adaptations that facilitate long-distance communication.

A comparison of speech intonation production and perception abilities of Farsi speaking cochlear implanted and normal hearing children

IntroductionCochlear implant prosthesis facilitates spoken language development and speech comprehension in children with severe-profound hearing loss. However, this prosthesis is limited in encoding information about fundamental frequency and pitch that are essentially for recognition of speech prosody. The purpose of the present study is to investigate the perception and production of intonation in cochlear implant children and comparison with normal hearing children. MethodThis study carried out on 25 cochlear implanted children and 50 children with normal hearing. First, using 10 action pictures statements and questions sentences were extracted. Fundamental frequency and pitch changes were identified using Praat software. Then, these sentences were judged by 7 adult listeners. In second stage 20 sentences were played for child and he/she determined whether it was in a question form or statement one. ResultsPerformance of cochlear implanted children in perception and production of intonation was significantly lower than children with normal hearing. The difference between fundamental frequency and pitch changes in cochlear implanted children and children with normal hearing was significant (P < 0/05). Cochlear implanted children performance in perception and production of intonation has significant correlation with child's age surgery and duration of prosthesis use (P < 0/05). DiscussionThe findings of the current study show that cochlear prostheses have limited application in facilitating the perception and production of intonation in cochlear implanted children. It should be noted that the child's age at the surgery and duration of prosthesis's use is important in reduction of this limitation. According to these findings, speech and language pathologists should consider intervention of intonation in treatment program of cochlear implanted children.

When speaker identity is unavoidable: Neural processing of speaker identity cues in natural speech

Speech sound acoustic properties vary largely across speakers and accents. When perceiving speech, adult listeners normally disregard non-linguistic variation caused by speaker or accent differences, in order to comprehend the linguistic message, e.g. to correctly identify a speech sound or a word. Here we tested whether the process of normalizing speaker and accent differences, facilitating the recognition of linguistic information, is found at the level of neural processing, and whether it is modulated by the listeners’ native language. In a multi-deviant oddball paradigm, native and nonnative speakers of Dutch were exposed to naturally-produced Dutch vowels varying in speaker, sex, accent, and phoneme identity. Unexpectedly, the analysis of mismatch negativity (MMN) amplitudes elicited by each type of change shows a large degree of early perceptual sensitivity to non-linguistic cues. This finding on perception of naturally-produced stimuli contrasts with previous studies examining the perception of synthetic stimuli wherein adult listeners automatically disregard acoustic cues to speaker identity. The present finding bears relevance to speech normalization theories, suggesting that at an unattended level of processing, listeners are indeed sensitive to changes in fundamental frequency in natural speech tokens.

Modeling and mitigation of excessive dynamic responses of wind turbines founded in warm permafrost

Field monitoring data provide evidence of excessive vibration on the wind turbines founded in warm permafrost (referring to soils frozen for more than two consecutive years with a temperature close to its melting point), which was attributed to resonance between the rotor and the tower-foundation system. This study presents a finite element (FE) model of the turbine-tower-foundation-soil system for analyzing causes of resonance and assessing effectiveness of mitigation measures. This model decouples the aerodynamic effects of the rotor from the turbine system. Aerodynamic simulation of the rotor was performed to provide wind thrust time series on the tower top. The lateral interaction between pile foundation and warm permafrost was modeled by distributed p-y springs and details on how to evaluate the permafrost p-y curves were provided. The FE model was used to investigate the sensitivity of wind turbine structural fundamental frequency to the permafrost temperature. It is found that, in addition to 9% seasonal change, the turbine-tower-foundation-soil fundamental frequency can decrease by 7% when the permafrost temperature increases from −2°C to 0°C. Analyses by using this model show that resonance can occur when the rotor speed is in the vicinity of the structural fundamental frequency, and increase the fatigue load on both the tower and foundation. The resonance is likely caused by the seasonal and long-term change in fundamental frequency of the turbine-tower-foundation-soil system and the inability of the controller to adjust its control parameters with time. Results show one tuned-mass-damper of 3% mass ratio is capable of reducing the tower peak acceleration and displacement during resonance by 50%, and reducing the peak shear and bending moment in the foundation by 40%. Adopting a controller with parameter updating capability together with using passive structural control techniques such as tuned-mass-dampers may be an effective control design strategy for wind turbines founded in warm permafrost.